The invention described herein relates to a device for verification and correction of the transverse dimensions of products in the form of a rod, in particular in machines for the manufacture of cigarettes and the like.
The substance of the following specification, which refers to a cigarette making machine, remains substantially valid likewise for a machine used in making cigarette filters.
The prior art embraces devices for verification of the transverse dimensins of such products, which are based on different operating principles. In British Pat. No. 888.478, a continuous rod turned out by a cigarette-making macine passes continuously endwise through a chamber supplied with gas (air) at constant pressure, which escapes by way of orifices through which the rod enters and leaves the chamber. Clearly, variation in the transverse dimensions of the rod causes variation in the area of the orifices via which air escapes, and as a result, of pressure inside the chamber; such pressure therefore gives an indication of the transverse dimensions of the length of rod occupying the chamber, at any given moment.
This pneumatic type of system does not offer a sufficient degree of precision however, as pressure levels measured within the chamber are influenced to a considerable extent by high porosity of the paper used in manufacture of the continuous cigarette rod, as well as by the speed at which the rod is conveyed.
The prior art further embraces devices such as that described in publication No. 0057992 for European Patent, wherein verification of the transverse dimensions of the cigarette rod is accomplished utilizing flexible feelers; one end of such a feeler is integral with a stationary support, whilst the remaining end is held in contact with the continuous rod. Means used to detect variation in tension of the feelers provide an output in the form of electrical signals, reflecting the circumferential dimensions of the rod, which can be utilized to implement such corrective measures as may be envisaged.
It will be clear enough that, in a device of this type, the sliding action of the feelers against the continuous rod may occasion damage to the rod itself, especially in ultra high speed cigarette making machines. What is more, the vibration of such feelers caused by sliding movement of the continuous rod, can give rise to errors in detection which in their turn are translated into errors in correction of the rod's circumference.
The object of the invention described herein it that of embodying a device for verification and correction of the transverse dimensions of cigarettes and similar products in the form of a continuous rod or in discrete lengths, which is able to eliminate all of the drawbacks connected with the prior art by adoption of a system that requires the use neither of pneumatic nor of mechanical means of detection.